HYDRUS-1D
Category Contaminant transport (1D)
Publisher  USDA Salinity Laboratory 
Platform Win3x
Status Freeware
Description HYDRUS-1D is a finite element model for simulating the one-dimensional movement of water, heat, and multiple solutes in variably saturated media. The program numerically solves the Richards' equation for saturated-unsaturated water flow and Fickian-based advection dispersion equations for heat and solute transport. The Flow equation incorporates a sink term to account for water uptake by plant roots. The Heat transport equation considers conduction as well as convection with flowing water. The Solute transport equations consider advective-dispersive transport in the liquid phase, and diffusion in the gaseous phase. The transport equations also include provisions for: Nonlinear and/or Nonequilibrium reactions between the solid and liquid phases; Linear equilibrium reactions between the liquid and gaseous phases; Zero order production, and Two First order degradation reactions. The program may be used to analyze water and solute movement in unsaturated, partially saturated, or fully saturated porous media. The flow region itself may be composed of non-uniform soils. Flow and transport can occur in the vertical, horizontal, or a generally inclined direction. The water flow part of the model can deal with (constant or time-varying) prescribed head and flux boundaries, boundaries controlled by atmospheric conditions, as well as free drainage boundary conditions. Soil surface boundary conditions may change during the simulation from prescribed flux to prescribed head type conditions (and vice versa). For solute transport the code supports both (constant and varying) prescribed concentration (Dirichlet or first-type) and concentration flux (Cauchy or third-type) boundary conditions. The dispersion coefficient includes terms reflecting the effects of molecular diffusion and tortuosity. It implements a Marquardt-Levenberg type parameter estimation technique for inverse estimation of selected soil hydraulic and/or solute transport and reaction parameters from measured transient or steady-state flow and/or transport data. Output also includes variable-versus-time plots, such as actual, potential and cumulative fluxes across boundaries or leaving the root zone. A free demonstration version is available on the WWW.
Cost Free on WWW
Data formats supported None stated
Supplier in United States of America  International Ground Water Modeling Center 
Supplier in United States of America  USDA Salinity Laboratory 

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